> ## Documentation Index > Fetch the complete documentation index at: https://docs.ca.cryptoprocessing.com/llms.txt > Use this file to discover all available pages before exploring further. # Exchange at a fixed rate > Execute an exchange using a valid quote from [/v2/exchange/calculate](/api-reference/endpoints/exchange-calculate). Send the request before the quote expires (`ts_release`), with the quote's currencies, the same amount field and amount, and its `price` exactly as returned. Each quote can be used for one request only. For every error this endpoint returns and what it means, see [API errors: Exchange at a fixed rate](https://docs.ca.cryptoprocessing.com/api-reference/errors.md#exchange-at-a-fixed-rate). ## OpenAPI ````yaml POST /v2/exchange/fixed openapi: 3.1.0 info: title: Merchant Backend V2 version: '1.0' description: Documentation for merchant backend processing endpoints servers: - url: https://app.ca.cryptoprocessing.com/api security: - xProcessingKey: [] tags: - name: Status - name: Balance - name: Currencies - name: Deposit addresses - name: Withdrawal - name: Exchange - name: Invoices - name: Transactions paths: /v2/exchange/fixed: post: tags: - Exchange summary: Exchange at a fixed exchange rate description: >- Execute an exchange using a valid quote from [/v2/exchange/calculate](/api-reference/endpoints/exchange-calculate). operationId: post-exchange-fixed parameters: - $ref: '#/components/parameters/XProcessingSignatureHeader' requestBody: content: application/json: schema: type: object properties: sender_currency: type: string description: >- Currency to exchange from. For a list of all available currencies, see [API currency codes](/api-reference/currency-codes). receiver_currency: type: string description: >- Currency to exchange to. For a list of all available currencies, see [API currency codes](/api-reference/currency-codes). sender_amount: oneOf: - type: string - type: number description: > The amount you want to exchange, in `sender_currency`, as a decimal string (for example, `"100"`) or a number. Include either this parameter or `receiver_amount`, not both. It must be the amount field and amount of the quote from `/v2/exchange/calculate`. Up to 8 decimal places. receiver_amount: oneOf: - type: string - type: number description: > The amount you want to receive, in `receiver_currency`, before the exchange fee, as a decimal string (for example, `"100"`) or a number. Include either this parameter or `sender_amount`, not both. It must be the amount field and amount of the quote from `/v2/exchange/calculate`. Up to 8 decimal places. foreign_id: type: string maxLength: 255 description: "Unique ID of this exchange in your system, up to\_255\_characters. It must be unique among your withdrawals and exchanges, and it's case-insensitive." price: oneOf: - type: string - type: number description: "The quote's `price` from `/v2/exchange/calculate` (units of `receiver_currency` for\_1\_unit of `sender_currency`), exactly as returned: a rounded value or one with extra trailing zeros doesn't match the quote." example: '0.99978134' required: - sender_currency - receiver_currency - foreign_id - price examples: "Convert 100\_USDC to USD": value: sender_currency: USDC receiver_currency: USD sender_amount: 100 foreign_id: exchange_123 price: '0.99978134' "Convert USDC to receive 100\_USD": value: sender_currency: USDC receiver_currency: USD receiver_amount: 100 foreign_id: exchange_123 price: '0.99980412' "Convert 0.01\_ETH to USDC": value: sender_currency: ETH receiver_currency: USDC sender_amount: '0.01' foreign_id: exchange_123 price: '2464.10773508' responses: '201': description: Created content: application/json: schema: type: object properties: data: type: object required: - id - foreign_id - type - sender_amount - sender_currency - receiver_amount - receiver_currency - fee_amount - fee_currency - price - status properties: id: type: integer description: Transaction ID. foreign_id: type: string description: This exchange's unique identifier in your system. type: type: string description: 'Transaction type: `exchange`.' sender_amount: type: string description: >- The amount exchanged from `sender_currency`: the `sender_amount` from the request, or the amount calculated for the `receiver_amount` you sent. It doesn't include the exchange fee (see `fee_amount`). sender_currency: type: string description: The currency being exchanged from. receiver_amount: type: string description: >- The amount the exchange gives in `receiver_currency`: the `receiver_amount` from the request, or the amount calculated for the `sender_amount` you sent. It's the amount before the exchange fee: if the fee is charged in `receiver_currency`, the amount added to your balance is `receiver_amount` − `fee_amount`. receiver_currency: type: string description: The currency being exchanged to. fee_amount: type: string description: >- The exchange fee. If it's charged in `sender_currency`, the amount taken from your balance is `sender_amount` + `fee_amount`; if it's charged in `receiver_currency`, the amount added to your balance is `receiver_amount` − `fee_amount`. `0.00000000` when no fee is charged, for example for an exchange between the same currency on different networks. fee_currency: type: string description: >- The currency the exchange fee is charged in: `sender_currency` or `receiver_currency`. price: type: string description: "The quoted exchange rate from `/v2/exchange/calculate`: units of `receiver_currency` for\_1\_unit of `sender_currency`." example: '0.99978134' status: type: string description: >- Exchange status. An [exchange callback](/api-reference/callbacks/exchange-callbacks) is sent when the status changes to `confirmed`. examples: "Convert 100\_USDC to USD": value: data: sender_currency: USDC sender_amount: '100.00000000' receiver_currency: USD receiver_amount: '99.97813400' fee_currency: USD fee_amount: '0.99978134' price: '0.99978134' id: 132541744 foreign_id: exchange_123 type: exchange status: processing "Convert USDC to receive 100\_USD": value: data: sender_currency: USDC sender_amount: '100.01959184' receiver_currency: USD receiver_amount: '100.00000000' fee_currency: USD fee_amount: '1.00000000' price: '0.99980412' id: 132541748 foreign_id: exchange_123 type: exchange status: processing "Convert 0.01\_ETH to USDC": value: data: sender_currency: ETH sender_amount: '0.01000000' receiver_currency: USDC receiver_amount: '24.64107735' fee_currency: USDC fee_amount: '0.02464107' price: '2464.10773508' id: 132541752 foreign_id: exchange_123 type: exchange status: processing '400': description: Bad Request. content: application/json: schema: $ref: '#/components/schemas/ValidationOrMalformedJson' examples: Quote expired, used or not matching: value: errors: price: Fix time is up. Exchange price is changed. Not enough balance: value: errors: sender_amount: >- Not enough balance. You have required at least Sender currency doesn't exist: value: errors: sender_currency: The selected sender currency is invalid. Receiver currency doesn't exist: value: errors: receiver_currency: The selected receiver currency is invalid. Same currency on both sides: value: errors: receiver_currency: >- The receiver currency and sender currency must be different. Pair not supported or currency not enabled: value: errors: sender_amount: Exchange is unavailable for given currencies Amount zero or negative: value: errors: sender_amount: The sender amount must be greater than 0. Amount not a number: value: errors: sender_amount: The sender amount must be a number. Both amounts sent: value: errors: receiver_amount: >- The receiver amount field can not be used when the sender amount field is presented. Missing fields: value: errors: sender_currency: The sender currency field is required. receiver_currency: The receiver currency field is required. receiver_amount: >- The receiver amount field is required when the sender amount field is not presented. foreign_id: The foreign id field is required. price: The price field is required. Price not a number: value: errors: price: The price must be a number. Sender currency not a string: value: errors: sender_currency: The sender currency must be a string. Foreign ID already used: value: errors: foreign_id: The foreign id has already been taken. "Foreign ID longer than\_255\_characters": value: errors: foreign_id: The foreign id may not be greater than 255 characters. Malformed JSON: value: error: Bad content format code: bad_content_format '403': $ref: '#/components/responses/HeaderAuthorization' '429': $ref: '#/components/responses/TooManyRequests' components: parameters: XProcessingSignatureHeader: name: X-Processing-Signature in: header required: true description: >- Hex-encoded HMAC-SHA512 signature of the request body, [generated using your secret key](/api-reference/authentication). schema: type: string schemas: ValidationOrMalformedJson: oneOf: - type: object title: ValidationError description: One or more request parameters failed validation. properties: errors: type: object description: > A map of request field names to a human-readable validation error message for that field. The exact set of possible keys and messages is endpoint-specific — see [API errors](/api-reference/errors#errors-by-endpoint) for the full reference. additionalProperties: type: string description: Human-readable validation error message for this field. - type: object title: MalformedJson description: >- The request body is not valid JSON or the Content-Type header is not set to `application/json`. properties: error: type: string code: type: string responses: HeaderAuthorization: description: | Forbidden content: application/json: schema: type: object properties: error: type: string description: Human-readable error message. code: type: string description: Error code. description: >- Invalid or missing headers, or the API key does not have access to the endpoint. Refer to [Errors](/api-reference/errors#general-errors) for troubleshooting steps. examples: Bad signature header: value: error: Bad signature header code: bad_header_signature API key does not have the required ability: value: error: The API key does not have access to this endpoint. code: api_key_ability_required No signature header: value: error: No signature header code: required_header_signature No key header: value: error: No key header code: required_header_key TooManyRequests: description: > Too Many Requests You sent too many requests in a short time. The limit is counted per API key, so requests from all your servers that use the same key count together. Wait before you send the request again, increasing the delay if you get `429` again, and handle this error by its status code, not by a particular response body. See [Too many requests](/api-reference/errors#too-many-requests-429-too-many-requests). securitySchemes: xProcessingKey: type: apiKey description: Your [API key](/merchant-administration/generate-and-activate-api-keys). in: header name: X-Processing-Key ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.